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adsmith
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 Posted: Mon Jul 25, 2005 4:46 pm Post subject: All the local-caching networks file systems? |
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I'd absolutely love to be running a disconnect-friendly local file caching network file system, (e.g., so a machine serving someone's home can hibernate for a while and the IMAP server can still access their mail directory, since it has been cached).
Here's what I've come across. Are these really the ONLY options?
1) OpenAFS: kernel-2.6 support improving. but many people say it's a huge pain to set up and maintain: https://forums.gentoo.org/viewtopic-t-331633-highlight-openafs.html
2) Intermezzo: has been out of the kernel for a few versions. deprecated.
3) CodaFS: was the predecessor of Intermezzo. long-dead.
4) zFS: http://www.haifa.il.ibm.com/projects/storage/zFS/. currently vapor-ware
5) NFSv4: not clear if it will have real caching or when it will be stable
Are these really the only options?? I find it hard to believe that there isn't some cleverly hacked kernel module which caches recently accessed files for any given filesystem. |
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nielchiano
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| Posted: Tue Jul 26, 2005 5:19 pm Post subject: Re: All the local-caching networks file systems? |
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| adsmith wrote: | | I find it hard to believe that there isn't some cleverly hacked kernel module which caches recently accessed files for any given filesystem. |
I think (not sure) that EVERY kernel does caching... but thet caching doesn't mean the same than your "caching".
What the kernel will do is:
on read: check if the file in cache is still up-to-date; if it is, get if from cache. if it isn't, get it on eth
on write: write it to eth and in the cache.
Because a file-system should be consistent for all machines accessing it... Your "caching" introduces a problem:
Imagin 3 machines: server, client1 & client2.
client1 and client2 have a FS mounted that resides on server. Server goes down; clients "cached" it.
client1 creates file "abc"
client2 creates file "abc", with different content
server comes online
What to do? use client1's file? client2's?
Something that might solve your problem is a regular rsync:
just COPY over the files you wish to have "cached" to a local directory, and setup rsync to send over changes (in both directions) every x minutes (depending on how "hot" you want to be)
Then setup a script that detects the server-offline-event and mounts your local "cache" over the net-mount. |
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adsmith
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Location: NC, USA
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| Posted: Tue Jul 26, 2005 5:26 pm Post subject: Re: All the local-caching networks file systems? |
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| nielchiano wrote: |
Something that might solve your problem is a regular rsync:
just COPY over the files you wish to have "cached" to a local directory, and setup rsync to send over changes (in both directions) every x minutes (depending on how "hot" you want to be)
Then setup a script that detects the server-offline-event and mounts your local "cache" over the net-mount. |
Yeah, I was thinking about that kind of solution last night. I bet with a cleverly constructed automount script controlling some links, it could be essentially transparent. Again, the conflict problem is always hard, but the problem is "what if I want to keep working when the fileserver goes away for a while" which shouldn't be too hard to solve |
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nielchiano
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Location: 50N 3E
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| Posted: Tue Jul 26, 2005 5:42 pm Post subject: Re: All the local-caching networks file systems? |
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| adsmith wrote: | | Again, the conflict problem is always hard, but the problem is "what if I want to keep working when the fileserver goes away for a while" which shouldn't be too hard to solve |
Well... it is....
As soon as you lose the server, you can't synchronize with other clients...
Also, to prepare to loose the server, you'd have to copy over the complete mount, which could take minutes or hours, depending on the amount of data and the network speed.
These 2 things seem "detail" but they're quite big... Windows has a solution, but he'll ask if both files changed; and he'll take around 30 minutes to copy my drive... |
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